GUESTS: LIEUTENANT DENNIS BEENE Unit commander for the Los Angeles County Sheriff's Emergency Operations Bureau. D'VERA COHN Staff writer for The Washington Post Author of the article, "The Reasonable Person's Y2K Guide." The arrest last week of a foreign national who was in possesion of bomb-making material has once again whipped up fears of disasters attending the arrival of the year 2000. Are fears of terrorist attacks and civil disasters unfounded? Join Katherine Lanpher and guests for a look at Y2K jitters— just how much should we be worried?